Continuous process for forming webs from fiber suspensions

ABSTRACT

The disclosure concerns a continuous method of forming webs from suspensions of long synthetic fibers wherein a body of water containing suspended fibers is established in a tank, said body of suspension is subjected to an upward directed field of gas jets, fibers and water are continuously fed to the tank at one side of said field, and suspension is continuously withdrawn from the tank over a weir at the opposite side of said field and passed directly to the breast box of a web-forming machine. The suspension may be subjected to the same action in each of a plurality of serially connected tanks as it flows through the tanks under the action of gravitational force.

United States Patent [1 1 [111 3,929,560

Holik et al. Dec. 30, 1975 [54] CONTINUOUS PROCESS FOR FORMING 3,021,255 2/1962 Sim son 162/156 WE ROM FIBER SUSPENSIONS 3,506,538 4/1970 Friedberg et al. 162/209 3,690,975 9/1972 Groombrldge.... 162/157 R [75] Inventors: Herbert Hohk, Ravensburg;K r1 3,716,449 2 1973 Gatward etal. 162/101 Mueller, Ringgenweiler, both of Germany Primary Examiner-S. Leon Bashore [73] Asstgnee: Escher Wyss G.m.b.H., Ravensburg, Assistant Examiner' peter i Germany Attorney, Agent, or FirmRobert A. Ostmann [22] Filed: Jan. 17, 1974 R1 63 C e f U Apphcamm Data The disclosure concerns a continuous method of form- 1 ommufmon of 1972 ing webs from suspensions of long synthetic fibers abandoned.

wherein a body of water containing suspended fibers 1S established in a tank, said body of suspension is sub- [30] Forelgn Apphcatlon Pnomy Data jected to an upward directed field of gas jets, fibers Dec. 9, 1971 Germany 2161101 and water are continuously fed to the tank at one i of said field, and suspension is continuously withdrawn [52] US. Cl; 162/157 R; 162/380 from the tank over a weir at the opposite Side of Said [51] Int. Cl. DZIF 11/00 field and passed directly to the breast box f a [58] Field of Search 162/101, 157 R, 157 C, forming machine The Suspension may be Subjected to 162/380, 341, 261; 425/4 C; the same action in each of a plurality of serially con- 261/DIG' 26; 241/18 19 nected tanks, as it flows through the tanks under the action of gravitational force. [56] References Cited UNITED STATES PATENTS 3" Claims, 2 Drawing Figures 2,772,603 12/1956 Waggoner 162/145 FIBERS AND WATER 'Q (g 5' 13. i 5 i 1 1 I j 2 I r I a i 1 S I s a 1 12-- E- 1 E 3 i x Q I I z a x I I I t N I 2 E E; \\\z) VII/11 1 TO BREAST BOX CONTINUOUS PROCESS FOR FORMING WEBS FROM FIBER SUSPENSIONS CROSS-REFERENCE TO RELATED APPLICATION This application is a continuation of application Ser. No. 311,483, filed Dec. 4, 1972, now abandoned.

BACKGROUND OF THE INVENTION The invention relates to a method for producing webs from a suspension of fibrous material, more especially long synthetic fibers.

To produce a fleece from longsynthetic fibres by the so-called wet method, the fibrous material is supplied in bundles of suitable length. It is necessary to put this material into suspension in water. To obtain a uniform fleece the individual fibres must be distributed as uniformly as possible in the suspension and the substance concentration, i.e. the ratio of the fibres to water, must not fluctuate in the course of time.

The use of the devices hitherto known in the paper making industry has been found sufficiently satisfactory with short synthetic fibres. The stacking and feeding of the fibre-water suspension hitherto used is also quite possible.

But with long synthetic fibres considerable difficulties occur, for once the long synthetic fibres are in suspension they very readily become tangled during the suspension operation and/or during stacking in the supply container. This prejudices the possibility of operating a continuous process. Therefore, the suspension operation must proceed batchwise, and the overall volumes required for this purpose, i.e. the suspensionproducing and storage containers, increase considerably. The substance concentration of the long synthetic fibres in the aqeous suspension must be very small, so that necessarily considerable suspension throughputs result.

A disadvantage of a hitherto known continuous process, wherein diffusers are used immediately in front of the breast box of a fleece machine, consists in that the substance concentration fluctuates in the course of time, since the long synthetic fibres introduced in bundles cannot be continuously supplied completely.

Moreover, the known devices for producing suspensions are also expensive and liable to develop trouble. They have complicated connecting pipes, injectors, pumps, agitating mechanisms and agitating pumps.

SUMMARY OF THE INVENTION The invention has as its object to provide a method of the type initially mentioned which operates continuously and as smoothly as possible without moved or rotating parts. According to the invention, this object is achieved by establishing in a tank a body of water in which the fibers are suspended, subjecting said body of suspension to an upward directed field of gas jets to agitate the suspension and thereby prevent entanglement of the fibers and encourage uniform distribution of same in the water, continuously feeding water and fibers to the tank at one side of the jet field, and continuously withdrawing suspension from the tank over a weir located at the opposite side of the jet field and conveying same to the breast box of the webforming machine.

A device particularly suitable for use in carrying out the method comprises a prismatic tank having a flat, horizontal bottom of rectangular shape which is formed, at least in part, with the through flow apertures which produce the field of gas jets. The inlet to the tank is a rectangular aperture located below the surface of the suspension, and both the inlet aperture and the outlet weir extend across the entire width of the tank.

The devices justmentioned can be assembled with others in a particularly simple and space-saving manner by arranging that an inlet duct is connected to the inlet aperture and an outlet duct to the outlet aperture, these ducts extending parallel with the walls comprising the apertures, and that a plurality of devices connected in series as regards the path of travel of the material are stacked on one another, the outlet duct of the particular device situated above opening into the inlet duct of the device situated below in each case, and the suspension flowing into the next device in each case because of gravitational force.

.The invention is described herein in detail with reference to the accompanying drawing in which:

FIG. 1 is a diagr amatic view, in longitudinal section, of an agitating tank used to carry out the method.

FIG. 2 is a schematic diagram illustrating the manner in which. tanks of the type shown in FIG. 1 may be stacked.

DESCRIPTION OF THE PREFERRED EMBODIMENT As shown inFIG. l, the tank 1 has side walls 2, 3 and 4 (the fourth side wall cannot be seen) and a bottom 5 provided with an inlet aperture 6 and an outlet aperture 7 for the fibrous material to be treated. For stirring the material there is arranged in the lower region of the tank 1 a stationary pneumatic agitating mechanism. A wall 8 of the agitating mechanism is provided with gas throughflow apertures 9 and acts as a boundary wall for the material. This wall 8, provided with gas throughflow apertures 9, of the pneumatic agitating mechanism is situated in the bottom 5 of the tank 1 and forms a part of the bottom 5. The wall 8 could also form the entire bottom 5.

The bottom 5 of tank 1 is flat and is situated substantially horizontally. The bottom 5 is rectangular and the tank 1 is prismatic in form. The inlet aperture 6 is situated below the surface 10 of the material in the tank 1 at its lower portion, and the outlet aperture 7 forms an overflow with an edge 13 in the upper portion of the tank 1. The inlet aperture 6 is situated at one side and the outlet aperture 7 in the opposite side of the chamber 1 therefrom, and in fact in the side walls 2 and 3 respectively which are situated at opposite sides of the bottom 5. The apertures 6 and 7 are rectangular and extend over the entire width of the particular wall concerned 2 or 3. The inlet aperture 6 is adjoined by an inlet duct 1 l and the outlet aperture 7 by an outlet duct 12. The ducts 11 and 12 are prismatic in shape, extend parallel to the side walls 2 and 3 comprising the apertures 6 and 7 and over the entire width of these walls 2 and 3. The overflow edge 13 of the outlet aperture 7 is rounded. The radius of the rounding is greater than the fibre length of the fibrous material to be treated. It is made smooth so that the fibres distributed in the suspension flow freely over this edge 13. Compressed air is introduced via a reducing valve 15 from a compressed air conduit (not shown) into a box 14. The air flows into the tank 1 through the gas throughflow apertures 9 of the wall 8. These jets of air move the material violently in the tank 1, with simultaneous expansion of the compressed air. The operation and the turbulent movement of the material which it produces breaks up the bunches of material and distributes the fibres uniformly in the suspension.

The average speed of the material being agitated brought about by the air jets issuing from the gas throughflow apertures 9 is greater than the average throughput speed of the material on its way through the tank 1 from the inlet aperture 6 to the outlet aperture 7. The desired treatment result in the tank 1 i.e. a homogenous suspension of the fibres with a balanced fibre content, can be achieved by adapting the following parameters to one another: namely the air pressure in the box 14, the form and distribution of gas through flow apertures 9 in the wall 8, and the throughput quantity of material passing through the tank 1.

Because'of its simple form, the tank 1 can be stacked in a space-saving manner with similar tanks to form a tower for suspension production using very simple connecting elements 18. Several tanks connected in series as regards the path of flow of the material are stacked on one another as shown in FIG. 2 and positioned so that the outlet duct 12 of the upper tank in each case opens into the inlet duct 11 of the tank situated below. The material to be treated is then introduced into the tower only by means of a single pump 19 into the uppermost tank. The suspension flows into the next tank in each case by virtue of gravitational force.

, A rectangular prismatic form of tank has been chosen and described as a constructional example of the invention, but the tank may also have other geometric basic shapes. Thus tank 1 may be, for example, cylindrcial in form, in which case the apertures 6 and 7 .would be in the form of segments of a circle and the ducts Hand 12 segments of cylinders. The bottom wouldbe circular.

We claim:

1. A continuous process for forming a web from long synthetic fibers comprising a. establishing in a tank a body of water in which the fibers are suspended;

b. subjecting said body of suspension to an upward directed field of gas jets to agitate the suspension and thereby prevent entaglement of the fibers and encourage uniform distribution of same in the water;

. continuously feeding a mixture water and fibers into the tank at one side of the jet field, below the surface of said body of suspension, and in the form of a stream which has a rectangular cross section and spans the entire width of the tank;

d. continuously withdrawing suspension from the tank over a weir located at the opposite side of the jet field and which spans the entire width of the tank; and i e. continuously conveying said withdrawn suspension directly to the breast box of a web-forming machine.

2. A process as defined in claim 1 in which said tank is the last of a plurality of similar tanks through which the suspension passes in series, each tank containing a body of suspension which is agitated by a field of said gas jets and the suspension entering each tank at one side of the field and being withdrawn therefrom over a weir located at the opposite side of the field, the tanks being located at different elevations so that the suspension. 

1. A CONTINUOUS PROCESS FOR FORMING A WEB FROM LONG SYNTHETIC FIBERS COMPRISING A. ESTABLISHING IN A TANK A BODY OF WATER IN WHICH THE FIBERS ARE SUSPENDED; B. SUBJECTING SAID BODY OF SUSPENSION TO AN UPWARD DIRECTED FIELD OF GAS JETS TO AGITATE THE SUSPENSION AND THEREBY PREVENT ENTAGELMENT OF THE FIBERS AND ENCOURAGE UNIFORM DISTRIBUTION OF SAME IN THE WATER; C. CONTINUOUSLY FEEDING A MIXTURE WATER AND FIBERS INTO THE TANK AT ONE SIDE OF THE JET FIELD, BELOW THE SURFACE OF SAID BODY OF SUSPENSION, AND IN THE FORM OF A STREAM WHICH HAS A RECTANGULAR CROSS SECTION AND SPANS THE ENTIRE WIDTH OF THE TANK; D. CONTINUOUSLY WITHDRAWING SUSPENSION FROM THE TANK OVER A WEIR LOCATED AT THE JOPPOSITE SIDE OF THE JET FIELD AND WHICH SPANS THE ENTIRE WIDTH OF THE TANK; AND
 2. A process as defined in claim 1 in which said tank is the last of a plurality of similar tanks through which the suspension passes in series, each tank containing a body of suspension which is agitated by a field of said gas jets and the suspension entering each tank at one side of the field and being withdrawn therefrom over a weir located at the opposite side of the field, the tanks being located at different elevations so that the suspension traverses the series solely under the action of gravitational force.
 3. A process as defined in claim 1 in which the average speed of the suspension effected by the gas jets is greater than the mean throughput speed of the suspension. 